The present invention relates to a hard coat film comprising a hard coat layer on a plastic base film. More specifically, the present invention relates to a hard coat film with excellent abrasion resistance and superior crack resistance, adhesion and resistance to the effects due to deformation, etc. of the plastic base film. The present invention is suitable as a touch panel surface protective film, for the surfaces of CRT, LCD, PDP and other displays, as well as household electric appliances.
In recent years, plastic products have been replacing glass products because of their workability and light weight. However, since plastic products are more prone to surface damage, they are usually covered with hard coat films in order to provide abrasion resistance. It is also becoming more common to cover conventional glass products with plastic films to prevent scattering when being broken, but because of their lack of hardness, hard coats are often formed over their surfaces.
A conventional hard coat film is usually produced by forming a thin coating film of a thermosetting resin or an ionizing radiation curing resin such as an ultraviolet curing resin, to about 3-15 .mu.m either directly on a plastic base film or via a primer layer of about 1 .mu.m.
However, while such conventional hard coat films have provided sufficient hardness, the fact that the coating films are of low thickness has led to the problem of deformation of the hard coat layers in response to deformation of the underlying plastic base films, resulting in lower overall hardness of the hard coat films, and their performance has therefore been unsatisfactory. For example, when polyethylene terephthalate films, which are widely used as plastic base films, are coated with hard coat films of ultraviolet curing paints to the thickness mentioned above, a pencil hardness of level 3H is common, but this does not approach the pencil hardness of glass which is 9H.
On the other hand, if the thickness of the hard coat layer is simply increased over the usual 3-15 .mu.m, the hardness of the resulting hard coat film is improved but this leads instead to the problem of easier cracking and peeling of the hard coat layer, accompanied by more curling of the hard coat film due to cure shrinkage. For this reason, it has been difficult by conventional techniques to obtain hard coat films with satisfactory properties for practical use.